Value of shares committed to be released under an Employee Stock Ownership Plan (ESOP).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 25
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=109244457&loc=d3e16721-113920

+ Details

Name:	us-gaap_AmortizationOfESOPAward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_DividendsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of paid and unpaid common stock dividends declared with the form of settlement in cash, stock and payment-in-kind (PIK).

+ References

+ Details

Name:	us-gaap_DividendsCommonStock
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of paid and unpaid preferred stock dividends declared with the form of settlement in cash, stock and payment-in-kind (PIK).

+ References

+ Details

Name:	us-gaap_DividendsPreferredStock
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

Name:	us-gaap_IncreaseDecreaseInStockholdersEquityRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118930883&loc=SL7669619-108580

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-URI http://asc.fasb.org/extlink&oid=116637391&loc=SL114874048-224260

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118930883&loc=SL7669625-108580

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(18))
-URI http://asc.fasb.org/extlink&oid=116637232&loc=SL114874131-224263

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(20))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

+ Details

Name:	us-gaap_NetIncomeLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount after tax and reclassification adjustments of other comprehensive income (loss).

+ References

+ Details

Name:	us-gaap_OtherComprehensiveIncomeLossNetOfTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Value, after forfeiture, of shares issued under share-based payment arrangement. Excludes employee stock ownership plan (ESOP).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

Name:	us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Value of treasury shares or units reissued. Excludes reissuance of shares or units in treasury for award under share-based payment arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_StockIssuedDuringPeriodValueTreasuryStockReissued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 4.E)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74512-122707

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(31))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(30))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_StockholdersEquity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of increase (decrease) in accumulated other comprehensive income (AOCI) for reclassification to retained earnings of tax effect from remeasurement of deferred tax pursuant to Tax Cuts and Jobs Act.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118930883&loc=SL116659650-108580

+ Details

Name:	us-gaap_TaxCutsAndJobsActOf2017ReclassificationFromAociToRetainedEarningsTaxEffect
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

+ References

+ Details

Name:	us-gaap_TreasuryStockValueAcquiredCostMethod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Millions	Total	Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning balance at Dec. 31, 2017	$ 10,216.3	$ 882.0	$ 408.6	$ 1,047.3	$ 9,685.1	$ (414.3)	$ (1,392.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification of Certain Tax Effects from AOCI					25.3	(25.3)
Net Income	381.6				381.6
Net Change	(66.1)					(66.1)
Dividends Declared:
Common Stock	(96.4)				(96.4)
Preferred Stock	(17.3)				(17.3)
Stock Options and Awards	102.5						102.5
Stock Purchased	(263.2)						(263.2)
Treasury Stock Transactions — Stock Options and Awards	(83.5)			(83.5)
Stock Options and Awards — Amortization	56.6			56.6
Ending balance at Mar. 31, 2018	10,226.0	882.0	408.6	1,020.4	9,973.8	(505.7)	(1,553.1)
Beginning balance at Dec. 31, 2017	10,216.3	882.0	408.6	1,047.3	9,685.1	(414.3)	(1,392.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification of Certain Tax Effects from AOCI						(25.3)
Net Income	1,146.5
Net Change	(87.3)					(87.3)
Ending balance at Sep. 30, 2018	10,364.5	882.0	408.6	1,055.3	10,496.3	(526.9)	(1,950.8)
Beginning balance at Mar. 31, 2018	10,226.0	882.0	408.6	1,020.4	9,973.8	(505.7)	(1,553.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	390.4				390.4
Net Change	(2.4)					(2.4)
Dividends Declared:
Common Stock	(95.8)				(95.8)
Preferred Stock	(5.9)				(5.9)
Stock Options and Awards	6.1						6.1
Stock Purchased	(190.6)						(190.6)
Treasury Stock Transactions — Stock Options and Awards	(3.2)			(3.2)
Stock Options and Awards — Amortization	33.0			33.0
Ending balance at Jun. 30, 2018	10,357.6	882.0	408.6	1,050.2	10,262.5	(508.1)	(1,737.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	374.5				374.5
Net Change	(18.8)					(18.8)
Dividends Declared:
Common Stock	(123.4)				(123.4)
Preferred Stock	(17.3)				(17.3)
Stock Options and Awards	22.7						22.7
Stock Purchased	(235.9)						(235.9)
Treasury Stock Transactions — Stock Options and Awards	(14.7)			(14.7)
Stock Options and Awards — Amortization	19.8			19.8
Ending balance at Sep. 30, 2018	10,364.5	882.0	408.6	1,055.3	10,496.3	(526.9)	(1,950.8)
Beginning balance at Dec. 31, 2018	10,508.3	882.0	408.6	1,068.5	10,776.8	(453.7)	(2,173.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	347.1				347.1
Net Change	108.4					108.4
Dividends Declared:
Common Stock	(133.7)				(133.7)
Preferred Stock	(17.3)				(17.3)
Stock Options and Awards	126.0						126.0
Stock Purchased	(257.4)						(257.4)
Treasury Stock Transactions — Stock Options and Awards	(120.5)			(120.5)
Stock Options and Awards — Amortization	55.3			55.3
Ending balance at Mar. 31, 2019	10,616.2	882.0	408.6	1,003.3	10,972.9	(345.3)	(2,305.3)
Beginning balance at Dec. 31, 2018	10,508.3	882.0	408.6	1,068.5	10,776.8	(453.7)	(2,173.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	1,121.1
Net Change	362.7					362.7
Dividends Declared:
Stock Purchased	(835.8)
Ending balance at Sep. 30, 2019	10,811.3	882.0	408.6	1,009.7	11,441.2	(91.0)	(2,839.2)
Beginning balance at Mar. 31, 2019	10,616.2	882.0	408.6	1,003.3	10,972.9	(345.3)	(2,305.3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	389.4				389.4
Net Change	185.5					185.5
Dividends Declared:
Common Stock	(130.9)				(130.9)
Preferred Stock	(5.9)				(5.9)
Stock Options and Awards	11.9						11.9
Stock Purchased	(271.2)						(271.2)
Treasury Stock Transactions — Stock Options and Awards	(8.3)			(8.3)
Stock Options and Awards — Amortization	18.8			18.8
Ending balance at Jun. 30, 2019	10,805.5	882.0	408.6	1,013.8	11,225.5	(159.8)	(2,564.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	384.6				384.6
Net Change	68.8					68.8
Dividends Declared:
Common Stock	(151.5)				(151.5)
Preferred Stock	(17.4)				(17.4)
Stock Options and Awards	32.6						32.6
Stock Purchased	(307.2)						(307.2)
Treasury Stock Transactions — Stock Options and Awards	(21.7)			(21.7)
Stock Options and Awards — Amortization	17.6			17.6
Ending balance at Sep. 30, 2019	$ 10,811.3	$ 882.0	$ 408.6	$ 1,009.7	$ 11,441.2	$ (91.0)	$ (2,839.2)